As shown in FIG. 3, the first high resolution microscope utilizing a tunnel phenomenon of electrons has been a field emission microscope FEM (Field Emission Microscope) in which electrons are radiated from a sharp needle tip, and the electrons produce a radiated electron image of the needle tip projected while being enlarged. This microscope is one utilizing an electric field radiation phenomenon in which, if a strong electric field is applied under a vacuum state, the electrons are emitted from a metallic conductor surface beyond a barrier of a surface potential by a quantum-mechanical tunnel effect, and is such that, by being so constituted that an electron radiation is performed from a tip surface of the metal formed like the needle toward a screen coated with a fluorescent material by an action of strong electric field, there is depicted the enlarged image of an emitted metal surface onto the fluorescent screen.
Although the atom cannot be seen because the resolution of the FEM is as low as about 1 nm, there is found a work function of a fine crystalline face on a semispherical face of the needle tip from an I-V characteristic of a negative voltage applied to the needle and a radiation current. If the applied voltage is switched from negative to positive and an inert gas of low pressure is introduced into a microscope body, the FEM operates as a field ion microscope FIM (Field Ion microscope) and it becomes possible to directly observe an atomic arrangement of the needle tip. The FIM has a characteristic capable of desorbing the surface atom of the needle tip in correct order as a positive ion by an electric field evaporation phenomenon. This phenomenon is utilized also in an atomic operation by a scanning tunneling microscope STM (Scanning Tunneling Microscope). If the desorbed ions are detected and identified one by one, a composition of the needle tip can be analyzed at an atomic level. On the bases of this concept, there has been developed a composite atom probe AP (Atom Probe) of a mass spectrometer capable of detecting a single ion and the FIM. The AP is the only apparatus capable of analyzing an electron state, an atomic arrangement and a composition distribution of the needle tip. Since the electric field evaporation advances in correct order in every atom layer from a surface first layer, by the AP it is possible to investigate a composition of every layer, a composition distribution of an interface and, in addition, an electron state change.
However, in this AP there is a strict restriction in a manufacture and shape of a sample, and a field capable of making the best use of its characteristic has been limited. It is a scanning atom probe (SAP: Scanning Atom Probe) that has been devised in order to break down this restriction. In order to select a specific needle from closely arranged needles and investigate its tip, an electric field must be localized to the needle tip. Whereupon, a grounded lead-out electrode of a fine funnel type is attached to an inside of the microscope body of the AP, and a positive voltage is applied to the planar sample in which the fine needles are closely arranged. Then, a high electric field is generated in a single needle tip existing just below a hole at the tip of lead-out electrode whose diameter is several μm to several tens μm, and the electric field is localized to a very narrow space between the hole and the needle tip. According to an electric field distribution calculation by a computer, even in a case where an apex angle of the needle tip is 90° and a radius of curvature of the tip is 50 nm, in the needle tip there is generated a high electric field demanded for the electric field radiation and the electric field evaporation. This fact shows the fact that, if there are irregularities of about several μm on the flat sample face, a tip of its protrusion can be analyzed. Since a surface to which no smoothing treatment has been applied, a corroded surface, a surface of a high efficiency catalyst, and the like are generally rich in their irregularities, it follows that these surfaces are investigated as they are. A basic structure of the SAP is shown in FIG. 4. The sample in a left end schematically shows a closely arranged type electric field radiation electron source. If the hole in the tip of the funnel type lead-out electrode approaches the needle tip on the sample face or a tip of the protrusion, the high electric field is generated in a very narrow region between the tip and the electrode, and the electrons radiated from the needle tip depict an FEM image on the screen. Further, if an inert image gas such as helium is introduced into the microscope body and the positive voltage is applied to the sample, a high resolution FIM image is depicted on the screen. Additionally, if the surface atoms are electric-field-evaporated by superposing a pulse voltage onto a steady-state voltage or irradiating a pulse laser light to the sample face, the surface atoms which have evaporated as positive ions pass through a survey hole in a screen center and enter into a refletron that is the mass spectrometer, and are detected one by one. The region to be analyzed is a region in which a diameter of its protrusion tip corresponding to the survey hole is several nano to several tens nano. If the analysis is continued, it is possible to investigate a composition change in a depth direction of this region by the resolution of one atom layer.
In this document, the sample in whose surface there exist the irregularities is made an analysis object, and there are shown the fact that, by finding out especially a convex portion and causing it to face the lead-out electrode, if the sample protrusion part is electric-field-evaporated in order from upper layer atoms to thereby draw out them as ions and they are detected by an ion detector (two-dimensional detection type) disposed behind the above lead-out electrode, an element analysis can be made by a time-of-flight measurement of each ion, and the fact that, since also a position information can be obtained, a three-dimensional composition analysis at the atomic level is possible.
On the other hand, in a case where the analysis object sample such as a semiconductor wafer for which there is a strong analysis need and a thin film magnetic head wafer called GMR or TMR is made the sample, it is frequent that the sample becomes a multilayer structure in which complicated patterns have been stacked, so that the structure of a portion that is desired to be analyzed varies. In order to analyze such an analysis object by using the AP, it is necessary to locally cut out a place that is desired to be analyzed to thereby cut out as a fine section in a tip of an acicular protrusion becoming the electrode in the tip and fix it. However, heretofore, there has existed only an old method of making the sample such as metal material acicular, and it has been very difficult to analyze a fine specified site by the AP. For this reason, as a method for this, it becomes indispensable to develop a preliminary working technique which works the sample itself into an acicular form. With a relation that it is the analysis at the atomic level, since an analysis object dimension becomes about 100 nm cubed, a technique for manufacturing at a pin point an analysis object part to an acicular sample becomes very important.
[Patent Document 1] Japanese Patent Application No. 2003-157120 Specification “Method of positioning a vertical position of a pickup sample and a sample having a mark showing a vertical direction”
[Non-Patent Document 1] By Morita Shozo “Scanning Probe Microscope: Base and Future Estimate”, Published by Maruzen on Feb. 10, 2000, 2.7 Scanning Atom Probe (SAP), 70-73 pages
[Non-Patent Document 2] Edited and Written by Nishikawa Osamu “Scanning Probe Microscope: from STM to SPM” Published by Maruzen on Mar. 30, 1998, Description on 8 page, and Table 1-2 Evaporation electric field intensities of various elements